Voxel-based mapping of cortical ischemic damage using Tc 99m L,L-ethyl cysteinate dimer SPECT in acute stroke.

BACKGROUND AND PURPOSE

When performed soon after stroke onset, single-photon emission computed tomography (SPFCT) with hexamethylpropylenamine oxime or Tc 99m L,L-ethyl cysteinate dimer (ECD) has significant added predictive value compared to neurological scores. With ECD SPECT, the degree of tracer uptake reduction predicts neurological recovery, and using a 40% threshold to characterize irreversibly damaged tissue (IDT), significant correlations have been observed. However, correlations between this uptake threshold and tissue outcomes have not been assessed. The purpose of this study was to validate the 40% ECD uptake threshold for the probabilistic mapping of IDT using an automatic, voxel-based approach.

METHODS

In 10 acute stroke patients, the authors first compared early ECD SPECT and late coregistered magnetic resonance imaging (MRI) data and assessed for IDT and "tissue at risk" (i.e., tissue with ECD uptake below and above 40%) the percentage of voxels ultimately infarcted and noninfarcted on late brain MRI. They then assessed the correlations between the volumes of brain tissue compartments and subsequent neurological recovery. Finally, to assess whether visual SPECT analysis is reliable compared to the more complex voxel-based approach, the authors compared the predictive value of the 2 methods for neurological recovery.

RESULTS

The majority of IDT voxels (average = 84%), defined by ECD uptake < 40%, evolved toward infarction, and 51.8% to 100% of at-risk voxels (average = 89%) escaped infarction. The extent of IDT correlated significantly with neurological recovery (P = .0009). There was good agreement between visual and voxel-based analyses (P = .0004).

CONCLUSION

The results support the validity of the ECD uptake thresholds chosen, suggesting that ECD uptake can reflect neuronal viability and that ECD SPECT can be useful for the early detection of potentially salvageable tissue and irreversible damage. These preliminary results encourage the use of this method in a clinical setting for fast decision making in choosing acute therapy.